Simple Machines. unit

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1 unit 3 Simple Machines Prior Knowledge The student has 1. found products of two single-digit factors using arrays 2. found a linear measure using inches and feet 3. added and subtracted three-digit numbers with renaming 4. found items in an encyclopedia 5. put words in alphabetical order 6. sequenced numbers through constructed graphs 8. identified geometric shapes 9. identified written text as a poem. Mathematics, Science and Language Objectives Mathematics The student will 1. calculate weight of an object in space 2. compute averages 3. record data 4. explore measurements of sides of a right triangle 5. use even and odd numbers to estimate 6. multiply and divide using two-digit numbers and three- or four-digit products 7. calculate the perimeter and, without using pi, the circumference of a circle. Science The student will 1. list and give examples of simple machines 2. give an example of a force, such as inertia, friction or gravity, overcome in work 3. construct at least one simple machine 4. predict the amount of force needed to move a resistance 5. name at least five inventors 6. associate at least three events of historical importance with the invention of three important machines. Language The student will 1. use related vocabulary to explain and describe the function of simple machines 2. use related books to illustrate, write, label and graph new concepts 3. write a book on simple machines 4. use related books in cooperative groups to help write a report on a simple machine 5. analyze related words for meaning.

2 2 Unit 3 Simple Machines SIMPLE MACHINES Grade 3 are devices that do Work and are called by using Force Tools that are used in to overcome Labor Friction Gravity by using tools such as Levers Wheel & Axle Inclined Plane Pulley Identified by class 1st 2nd 3rd such as such as such as such as such as such as Crowbar Tongs Nutcracker Wheelbarrow Wedges Screws Fixed Movable that lead to Inventions C O N C E P T W E B

3 Unit 3 Simple Machines 3 V O C A B U L A R Y machine force friction pliers máquina fuerza fricción pinzas, alicates, o tenazas gravity effort resistance fulcrum gravedad esfuerzo resistencia fulcro pulley inclined plane fixed hoist polea plano inclinado fijo, fija izar wheel and axle tool device lever rueda y eje herramienta aparato palanca bicycle slide invention broom bicicleta resbaladero invención escoba scissors wheelbarrow tweezers food press tijeras carrucha pinzas prensa para cocinar crowbar nutcracker hammer barra cascanuez martillo seesaw pound nail sube-y-baja martillar clavo Teacher Background Information The world we live in is constantly exerting different forces on itself and on the beings that inhabit it. Forces make objects move; forces make objects change their direction; and forces make objects stop. These forces appear to be more important when they are acting on us as individuals, or when we want to use these forces to change our environment to suit our likes. Over long periods of time humans have learned how these forces work, and to some degree we have these forces under our control. Granted, we may be novices in the use of these forces, but we have been able to use them to accomplish many things. For example, humans have changed their environment in many ways, by building structures for shelter, by clearing land and obtaining and conserving water to grow food on a relatively dependable cycle. This has been accomplished by sawing and lifting large trees, driving nails through hard wood, removing large rocks and pulling out large stumps. All of the changes have come about as humans have learned to control these forces as push s or pull s. When we accomplish a change, such as raising a heavy rock or chopping down a tree, we accomplish work. Work produces change and change is the result of work.

4 4 Unit 3 Simple Machines Humans could not have accomplished many of these changes by using only the energy our relatively weak bodies can exert. Humans, however, have used their brains to design devices that have helped in bringing about these changes. A machine is but one example of how human intelligence has helped in making our lives on earth easier. A machine is, in a very general sense, a combination of parts we use to overcome a resistance (which is also a force, like a large rock that needs to be removed) by transferring or transforming energy, usually that exerted by a human being. There are fundamentally three basic machines the lever, the inclined plane and the wheel and axle. We sometimes refer to other combinations as simple machines, and these appear somewhat more complicated but in reality are combinations of the three basics. In this unit, we will look at two major forces that machines help us overcome friction and gravity. Inertia, on the other hand, is a characteristic of matter it is the resistance of mass to being in motion or removed from motion. Consequently, if we want to move matter, or a mass, which is expressed as weight, we need to exert force on that matter to overcome inertia as well as friction and/or gravity. Usually, the forces we want to overcome we call the resistance. The forces we use to overcome the resistance we call the effort. When we do work, we use energy. Energy changes in form, but it does not disappear. In using simple machines for human work, energy transfers from one object to another, or it changes in form as sound, heat or light energy. Understanding how simple machines function is a big step in understanding how much of the world around us functions even in modern times, because the nature of matter and energy has not changed only our understanding of it has. Current emphasis on the importance of elementary students learning and applying basic concepts of probability and statistics suggests that a fundamental concept such as the average be introduced at an early opportunity using intuitive approaches. The following set of activities has been designed and implemented at a third grade level with bilingual children whose education emphasizes language development as a major strategy to develop mathematics and science concepts. The intuitive notion in this strategy is that finding the average is similar to taking individual sets, whose cardinal numbers we know, and then making the sets even (i.e., make the stacks level). The teacher may want to begin the lesson by discussing the idea of making stacks, or sets, level. Showing two or three stacks having different numbers of chips, the teacher points out that the stacks have different heights. These stacks are uneven (i.e., not level). The stacks are to have the same heights. The students, in a problem-solving approach, discover how to make any number of uneven stacks into even or level stacks. Introduce the following activities with these notions in mind. Studying a machine created to help humans work is an important approach for introducing students to relatively sophisticated ideas of inertia, which is a property of matter, and ideas of forces that act upon matter. Concepts of friction and gravity lead to the more complex ideas that students will be able to understand when they have this background supported by experiences that relate science to the real world.

5 Unit 3 Simple Machines 5 LESSON ONE BIG IDEAS LESSON TWO BIG IDEAS LESSON THREE BIG IDEAS LESSON FOUR BIG IDEAS LESSON FIVE BIG IDEAS LESSON SIX BIG IDEAS LESSON SEVEN BIG IDEAS L E S S O N F O C U S Simple Machines Simple machines are devices that help us do work. When we do work, we use energy; energy transfers or transforms, but it does not disappear. Force and Work When we do work we use a force to overcome inertia, friction or gravity. We can measure work. A Crowbar The three different kinds of levers have different fulcrum locations. We calculate work using multiplication. A Bicycle A wheel and axle is a machine that rolls its load by decreasing friction. We can estimate the perimeter (circumference) of a wheel. A Slide An inclined plane is a machine that changes the direction that force is applied and that helps decrease the effect of gravity, though it may increase friction. Different types of inclined planes form right triangles. A Pulley A pulleys helps us change the direction of a force. A pulley transfers energy through distance (or nothing in nature is free). Inventions An invention is a combination of simple machines, for example, a footpedal sewing machine or a car.

6 6 Unit 3 Simple Machines O B J E C T I V E G R I D Lessons Mathematics Objectives 1. calculate weight of an object in space 2. compute averages 3. record data 4. explore measurements of sides of a right triangle 5. use even and odd numbers to estimate 6. multiply and divide using 2-digit numbers and 3- or 4-digit products 7. calculate the perimeter and, without using pi, the circumference of a circle. Science Objectives 1. list and give examples of simple machines 2. give an example of a force, such as inertia, friction or gravity, overcome in work 3. construct at least one simple machine 4. predict amount of force needed to move a resistance 5. name at least 5 inventors 6. associate at least 3 events of historical importance with the invention of 3 important machines. Language Objectives 1. use related vocabulary to explain and describe the function of simple machines 2. use related books to illustrate, write, label and graph new concepts 3. write a book on simple machines 4. use related books in cooperative groups 5. analyze related words for meaning.

7 Unit 3 Simple Machines 7 LESSON 1 Simple Machines BIG IDEAS Simple machines are devices that help us do work. When we do work we use energy; energy transfers or transforms, but it does not disappear. Whole Group Work Books: Simple Machines by A. Horvatic and Family Pictures by C. L. Garza Filmstrip: Discovering Simple Machines Pictures of people involved in different activities such as playing, riding bikes, sharpening pencils, etc. Long stick or cut-off broom handle For mobile: yarn, paper clips, rulers, straws, magazines, paper Word tags: force, gravity, friction, machine, simple, inertia, energy, work, transfer, transform People have to work to have the things they need, such as food, shelter and houses. People, however, have always tried to find ways to get help to do this work. Early people trained and used animals to help them work. One reason is that animals for example, oxen are stronger and have more energy than humans, therefore exerting more force. At a later date, however, people invented simple devices called machines to exert, transfer or transform energy to do work for us. All of us today still use our own energy to get work done; but we have also used our brains to help us do some things that we might not be able to do by ourselves. For example: Let s ask Sandra (a small girl who has trouble doing the task) to lift this heavy box to the top of this table. Sandra, can you do it? No, it s too heavy? Okay, then let s try this experiment. Students do Activity Let s Share the Work. After the demonstration, tell students that one of the important discoveries in the history of human beings was the development of our ability to use objects found in our environment to help us work. We will also explore some important ideas related to energy in order to understand how to make work easier. Show students the picture of the person moving a large rock. Tell them to observe that a small person can move a big rock if she uses a strong, long stick. Ask Sandra if she thinks she could raise the rock if she had a long stick. Again, ask for suggestions. Encountering the Idea Exploring the Idea Getting the Idea

8 8 Unit 3 Simple Machines When the girl in the picture pushes down on the stick to move the rock, she is using energy. She is also doing work. Why? She is changing the place where the big rock was resting to a place higher up in the air with the aid of the stick. What does the big rock do to the stick? (It is pushing down with its mass.) Yes, the rock is a force pushing down on the stick. When the girl pushes down on the stick under the big rock, the stick pivots on a small rock or some other object, transferring the energy from the girl through the stick into the big rock and making the big rock move up. big rock down small rock up Organizing the Idea What happens if the girl lets go of the stick? The rock will fall and transform its energy by crashing down with a noise. The rock transfers its energy by making a hole in the ground, making a loud noise as it hits and heating the ground around it. The energy transfers from the girl to the rock, and then if the rock falls, the energy goes back from the rock as sound, heat or motion energy. Now, let s look at these magazine pictures. These people are all doing something. Let s name the activities. Each picture shows a force applied to something. Let s name the forces applied and how they are applied. Devices that people use to help them work we call machines.the strong stick together with the small rock shown in this picture form an example of a simple machine we call a lever. People do work by exerting a force on something. The machine transforms or transfers the energy to do work. The girl pushed down and the big rock lifted up. Let s all do the same thing using a pencil to lift a book. What did you use as a pivot, or substitute for the rock? At the Mathematics Center, students complete Activity A Paper Fan is a Simple Machine. 1. Filmstrip: Discovering Simple Machines. 2. Students use the book Family Pictures to find examples of simple machines in the illustrations. 3. At the Art Center the students complete Activity Simple Machines Mobile. At the Language Center, students 1. practice dictionary skills by spelling, syllabication, naming parts of speech, multiple meanings and use of the pronunciation key with new words from this unit (force, gravity, friction) 2. analyze words related to the ideas they will learn in this unit. Tell the students that to analyze means to take words apart and then to study the parts to see how they fit to make a new word.

9 Unit 3 Simple Machines 9 Uni - corn. (Show picture and write on chalkboard.) What does uni mean? What does it remind you of in Spanish? (One.) What is corn? In Spanish, "cuerno is horn. Then, a unicorn is a one-horn animal. Let s look at bicycle." (Show picture, write it on chalkboard.) What do you think cycle means? (Circle, wheel.) What about bi? (Two.) A bicycle has two wheels. A unicycle? (Shows picture.) What is a tricycle? Tripod? Triplets? Triangle? Look in your dictionaries to find other words that start with the prefixes uni, bi, or tri and then make a list. Report to the class after we have completed work at the learning centers. Describe how a nutcracker works. Where does the energy come from that cracks the nut? What is the work that is done? Define and/or illustrate a machine. Try to use words such as energy, work and friction or gravity in your definition. List of Activities for this Lesson Let s Share the Work A Paper Fan Is a Simple Machine Simple Machines Mobile Applying the Idea Closure and Assessment

10 10 Unit 3 Simple Machines Getting the Idea ACTIVITY Let s Share the Work Objective The student understands the concept of work as using a force to move a mass over a distance and gives an example of work. Large open box with several heavy books or other objects in it Procedures Students working in small groups help Sandra decide how to lift the box, but before we help her, let s try to see if we can: 1. have the groups look for one way to compare the task 2. give, write down and implement different suggestions; for example, two large students lift the box (or three or four students) 3. consider all the suggestions and give opinions as to which would be easier, more efficient, etc. One suggestion could be that Sandra take one book out of the box at a time until she can lift the box by herself, then put all the books back in the box. 1. Ask the students: Regardless of which way we solved the problem, was the amount of work done the same? (Yes. Regardless of how we did it, we lifted the heavy box with its contents to the table.) 2. Did the box weigh the same when two, three or four people lifted it? (Yes, it weighed the same, but the people shared the work.) 3. When two people lifted the box, how much work did each one do? (1/2 each.) 4. When three people lifted the box, how much work did each one do? (1/3 each.) 5. When Sandra did the work by herself, how much work did she do? (All of it.) 6. When you were lifting the box to the table what force were you working against? (Gravity.) One other thing that we have to remember: When we do work we use energy. 7. Who used energy in doing the work of lifting the box? (Yes, everyone who helped had to use energy to get the work done.) Work, then, is defined as moving a mass over a distance. 8. What work was done here? (This box, this mass, we raised (moved) 38 inches.)

11 Unit 3 Simple Machines 11 ACTIVITY A Paper Fan Is a Simple Machine Objective The student constructs a paper fan and describes it as a simple machine, indicating where the resistance is exerted, where the force is applied and where the fulcrum is located. Sheet of construction paper; transparent tape; crayons Procedures 1. Decorate an 8 1/2 X 11 sheet of paper in the style of a fan. 2. Fold the sheet of 8 1/2 X 11 paper in half along the width (the 8 1/2 side), then 1/2 again, 1/2 again and 1/2 again, making sharp creases. 3. There will be 16 strips of paper (or 15 creases). 4. Unfold the paper and refold it in an accordion pleat. 5. Secure with transparent tape one end of the newly folded paper. 6. Open up the unsecured part as a fan. 7. As you fan yourself, locate the resistance, the force applied to overcome the resistance and the fulcrum. 8. Discuss this with your group. When you think you have the correct answers, report to the class or to your teacher, giving them the reasons for your answers. This paper fan is an example of a machine. What work does it do? (Air has mass and it moved, therefore the fan does work.) Getting the Idea

12 12 Unit 3 Simple Machines ACTIVITY Simple Machines Mobile Objective Students draw or identify simple machines from pictures in magazines. Five to six pieces of yarn centimeters long; paper clips; cutouts of simple machines on different-color tagboard 1 ; drinking straws in different lengths depending on the shape you want to give to the mobile; magazines Procedures 1. Cut several pieces of yarn 20 to 22 centimeters long. 2. Tie one end of each piece of string to a paper clip. 3. Select machines to depict and cut out of tagboard to hang. 4. Select a place to hang the mobile. 5. Hang the objects from a drinking straw with yarn. Loop the yarn once around the straw. Make half a knot. Pull the yarn tight. Clip the paper clip to each object. 6. Balance the objects by sliding the yarn on the straw. 7. Change the clip on each cutout as needed to make the mobile attractive. 8. Suggest to the students that they design and construct other mobiles, as they have time. 1 Students can cut pictures of simple machines out of magazines and glue pictures on tagboard to use in the mobile, or they can draw their own designs of simple machines on pieces of tagboard and use those for the mobile.

13 Unit 3 Simple Machines 13 LESSON 2 Forces and Work BIG IDEAS When we do work we use a force to overcome inertia, friction or gravity. We can measure work. Whole Group Work Piece of carpet about three feet x three feet Blow dryer Book or song: Wheels on the Bus by P. O. Zelinsky Books: Friction by E. Victor, Force: The Power Behind Movement by E. Laithwaite, and Up, Down, and Around: The Force of Gravity by M. Selsam Word tags: force, gravity, friction, machine, simple, inertia, energy, work, transfer, transform, resistance A force is a push or a pull. We cannot do work without a force either pushing or pulling on something; machines help people exert energy in special ways to help them do work. We all know what work is we move something or pick it up. Many of us do not like to do hard work if there is a machine that will help us do it more easily and quickly. Let s read Wheels on the Bus. Why are the people riding the bus? (To get somewhere, go shopping, not have to walk.) Why don t they walk? (It s too tiring.) Why is it tiring? (It s very far, takes too long; bus covers distance in shorter time.) Bertha, please walk across the room. Are you doing work? Yes, how do you know you are doing work? For one, you are using energy; for another, you are moving your weight across the room. Now, suppose that I ask you to walk and carry this 10-pound load for one mile. That would really be a lot of work because you would not only have to move your body that has mass and that weighs around 90 pounds because gravity is pulling on it, but you would have to carry the load that also has mass and that weighs 10 pounds. You would have to carry 100 pounds for one mile. Now, let s think about this. Raul, please pull your desk across the floor. Can you do it? Now, place the desk on top of this piece of carpet and pull the desk across the carpet. Can you do it? Why was it easier to pull the desk across the floor? What did you feel when you were pulling the desk across the carpet? Yes, the carpet was making it stick. (If a student says that the carpet makes friction, acknowledge the comment and say that it is correct and will be discussed later in the lesson.) In this lesson we are going to discover how work, energy, force, friction and gravity relate. Before you go to your learning centers, we are going to do some interesting kinds of things that might surprise you. Encountering the Idea

14 14 Unit 3 Simple Machines Exploring the Idea Getting the Idea The students complete Activity Kickball. Back in class after playing kickball, students identify when they used their body force (which is also the inertia of the human body put into motion by the body s muscles) and gravity during the game. They complete the Getting the Idea phase of the activity. Now, let s try a new situation. Let s use this eraser to erase this word. (Write a word in pencil on a piece of paper.) When I rub the word with the eraser, the eraser rubs out the word. Feel the eraser; how does it feel? (It got hot and so did the paper.) Friction is a force and can transfer energy of movement (moving the eraser back and forth) to heat energy. Let s put our hands together, squeeze them and rub. What happens? Why? (Friction transforms motion energy into heat.) Tell students that we do work when we move an object that has mass. Mass has the characteristic of inertia. Roll a heavy object (a bowling ball); a student stops it but uses force to stop it. Roll the object again; this time a student changes the direction of the ball; again a student has to use force to do it. The students describe the force needed to move, stop and change the direction of the rolling object. At the Mathematics Center, the students 1. complete the Activity Fractions 2. complete Activity Friction of Surfaces 3. complete Activity Measuring Work. We have studied two forces today. What are they? Gravity and friction. When we overcome a force, such as gravity or friction, we are doing work. When we work, we are usually moving against a force through a distance. Let s give some examples of the work we did in the experiments. 1. What work did Bertha do in walking across the room? Yes, she moved her weight by working against friction, but she also worked against her own inertia. Inertia is the property of matter that resists change from being at rest or from being in motion. For example, if we place a piece of wood on a table, it will stay there until some force, like a person pulling on the rubber band or a strong gust of wind, moves it. (Demonstrate with a blow dryer, if possible.) So, when we move our bodies, we are working against the inertia of our bodies. When we carry a load, we have to move the load against its own inertia. 2. What work did you do when you pulled the chair across the floor? Yes, you moved against the inertia of the chair and also against the friction of the floor. 3. What work did you do when you pulled the chair across the carpet? Yes, you used energy to move against the inertia of the chair but also against the greater friction of the carpet. 4. What work did you do when you were pulling on the wood block? Tell students that sometimes the force that we overcome in doing work is the resistance. Remember a resistance is always a force that is opposing the effort we exert when we do work. For example, when I shovel some dirt from the bottom of a hole to the top of the hole, what is the resistance? Yes, the dirt is the resistance but also the shovel, because I have to move both of them against their own inertia, and in bringing up the dirt I have to overcome gravity too.

15 Unit 3 Simple Machines 15 At the Writing Center, assign each student group to read in reference books on energy, force, friction, gravity, resistance, inertia and work. They report to the class and define and illustrate each term in their own words. Using new words from the unit force, gravity, friction, machine, simple, inertia, energy and work write a paragraph using each of the words or make an illustrated dictionary by putting all the words in alphabetical order, defining each (you may look in a dictionary to make sure you get the correct definition) and illustrating the word or make an illustrated dictionary by putting all the words in alphabetical order, defining each (you may look in a dictionary to make sure you get the correct definition) and constructing a model of the word. Design a rocket ship to go into space. Decide what forces you will have to overcome, then design the craft to overcome these forces. Oral Interview Use your pencil as a tool to write. Write your name and as you write decide whether the pencil is a simple machine. Explain, verbally, why you think it is, or why you think it is not. If you prefer, you may explain your reasons to your group, and then after the group thinks you have the correct answer, explain it to your teacher. List of Activities for this Lesson Kickball Fractions Friction of Surfaces Measuring Work Organizing the Idea Applying the Idea Closure and Assessment

16 16 Unit 3 Simple Machines Getting the Idea ACTIVITY Kickball Objective Students experience three forces in playing kickball; students say that inertia, friction and gravity are forces operating in playing kickball. Kickball Pictures of people involved in different activities such as playing, riding bikes, sharpening pencils, etc. Procedures Students play a game of kickball. As students play, the teacher directs their attention to the energy they are using in playing ball. They have to have energy to kick the ball with force that they need to move the ball; they need the force to change the direction of the ball, and need force to stop the ball. Tell them that after the game you will ask them about the three different kinds of forces they are using in playing. After the game: 1. Tell students that a force is a push or a pull. What is the push in playing when you kick the ball? Your foot is a push against the ball. What is the force your foot feels when you kick it? You are kicking against the mass, the matter of the ball. The resistance you feel in kicking the ball is the inertia of the ball. 2. Ask the students what happened when they kicked the ball into the air. Was there another force acting on the ball? Yes, gravity pulled it down. Gravity is a pull, so gravity is also a force. When you stop a falling ball with your foot or your head, how can you tell that gravity is a force? ( It hits you hard, and you know it is a force because it pushes against you.) When a ball falls, we say that gravity pulled it and caused it to fall. 3. What happens when you roll a ball on tall grass? Does it go fast or slow? What causes it to slow down? (Friction.) Is friction a force? How do you know? (It pushed against the ball and made it stop.) Energy is what we need to exert a force. Display pictures of people involved in different activities such as playing, riding bikes, sharpening pencils, etc. Define energy, force, gravity and friction while pointing to pictures illustrating each. Have students identify other examples of the forces found in the pictures.

17 Unit 3 Simple Machines 17 ACTIVITY Fractions Objective The student use fractions to measure the length of an object to the nearest oneeighth of an inch. Rulers or measuring tapes marked in inches Laminated strips of thick paper (one inch by 13 inches), marked in inches to simulate a ruler Various objects to measure length One screwdriver (or some other tool) of the same size for each group Each of you will work in groups to find the lengths of these objects. First, however, each group finds the length of the screwdriver. Using the laminated rulers, each group measures the same-size tool. What is the length of the screwdriver? Some of you are saying it is eight inches, others say it is inches and some of you say it is closer to nine inches. It is true that the screwdriver is longer than eight inches, but is it shorter than nine inches? Yes, but what do you suppose we can do to get closer to its true measurement? Yes, one way is to cut the inches into smaller parts such as 1 2 or 1 4. Let s use the strips to measure the length of the screwdriver again. Take your marker and draw how you would cut the inch to get closer to the length of the screwdriver. Encountering the Idea Exploring the Idea Sometimes when we have to measure the length of objects, we want to get as close as possible to their true length. To do that we cut the unit of length into smaller equal parts to help us. Some of you cut the unit into halves, others into fourths and some into eighths. Some of you said the screwdriver measured inches, and some of you said it measured, inches. How can you show with your strips if 1 2 and 2 4 are the same? We say that 1 4 and 3 12 are two ways of showing the same fraction. We say that they are equivalent fractions. Other names for 1 4 are 5 20, 6 24, and what others? Can Getting the Idea

18 18 Unit 3 Simple Machines Organizing the Idea Applying the Idea you find a pattern between the numerator and the denominator for all the fractions that are other names for 1 4? Students mark their number strips with 1 2, 1 3, 1 4 and mark their equivalents on the strips. For example, the students mark 2 4, 3 6 etc. to show the different names of the basic fraction 1 2. Fractions are numbers we can use when we want to talk about parts of things. In the activities below, you can see that there are many ways to use fractions. 1. Suppose you have a candy bar that you want to share with your friend. You can cut the candy bar in half like this (1). You can take the white part and your friend the brown part. Are the two parts the same? You can also divide the candy like this (2). You take two parts white and your friend takes two parts brown (1) (2) (3) (4) 2. Maria s mother told her to go to the store to buy one pound of pecans for a cake she was making. At the store, the clerk told Maria that all she had were bags of 1 4 pound each. What should Maria do? 3. Are 2 4, 3 6 and 4 8 all other names for 1 2? Draw other different pictures for 1 2 and write fractions for those pictures. 4. Suppose there are 12 people on a team. Three players are injured. What fraction, or what part, of the team is injured? ( 3 12, and also 1 4). Assessing the Idea 1. In your own words, tell what equivalent fractions are. 2. Use the laminated strips to show some equivalent fractions for 2 3 and 1 8. Using these paper clips (some are bent to the point that we can no longer use them), tell the fraction of the paper clips that we can t use. 3. Write three equivalent fractions for 3 5, 1 4, 5 10.

19 Unit 3 Simple Machines 19 ACTIVITY Friction of Surfaces Objective The student demonstrates that overcoming a force such as friction is work. Two wood blocks of the same size; thumbtacks; thin rubber band; paper clips; sheets of sandpaper; waxed paper; aluminum foil; construction paper; centimeter ruler Procedures 1. Place a wooden block on a wood surface. 2. Fasten a rubber band to it with a thumb tack. 3. Hook the rubber band with an opened paper clip. 4. Hold the rubber band end over the end of a ruler. 5. Pull the rubber band very slowly. Observe and record where the rubber band end is over the ruler. 6. Measure how far the band stretches before the block moves. Make the reading before the block begins to move. Read the ruler to the nearest centimeter. 7. Perform the same experiment on other surfaces. wood block rubber band ruler Discussion 1. What mass did we move? 2. What distance did the mass move? 3. What work did we do in this experiment? 4. What force did you overcome when you did this work?

20 20 Unit 3 Simple Machines ACTIVITY Measuring Work Objective Students calculate work done by moving various weights over a distance. Plastic bag filled with dirt to weigh a pound Foot ruler or tape ruler to use to measure distances across the room Scale to weigh various objects in the classroom Procedures 1. Stand the ruler on the table or the floor. 2. Raise the one-pound weight to the top of the ruler. 3. Raise the one-pound weight six inches. How much work did you do? (1/2 foot-pound.) 4. Raise the weight two feet. How much work did you do this time? (two footpounds.) 5. Select various objects in the room. Weigh them. Determine the amount of work you do in carrying that object a measured distance. 6. Each person weighs herself/himself. Climb a set of stairs. How much work did you do to get to the top? Getting the Idea Finding the amount of work you do in climbing stairs is a little tricky. To find the work you did, did you multiply your weight times the distance along the line along the steps? NOT! There is a small problem in calculating the work in this situation because if you climbed a set of stairs you can t measure the distance along the stairs but can measure from the floor to the top of the stairs (the dark line), as in the picture shown above. If you can t climb up the side of the stairs to measure the height, then you need to find the vertical distance another way. The students work in their groups to find a solution. If you haven t figured it out, try this. Measure the height of each step and add to get the total vertical distance. Or if all the steps are the same height, measure one of them and multiply by the number of steps! Remember: The amount of work you do to raise one pound a distance of one foot straight up is called one foot-pound. You did foot-pounds of work in walking up the set of stairs.

21 Unit 3 Simple Machines 21 Suppose you need to carry 100 pounds of computer paper up the set of stairs in the problem above. Find one way to make your work easier. Applying the Idea 1. What is work? Give examples. 2. What two things do you need in order to do work? 3. What provides the force when you are riding a bicycle? In a car? 4. Write your own definition of work. Assessing the Idea

22 22 Unit 3 Simple Machines LESSON 3 A Crowbar BIG IDEAS The three different kinds of levers have different fulcrum or pivot locations. We calculate work using multiplication. Whole Group Work Encountering the Idea Exploring the Idea Organizing the Idea Applying the Idea As many as possible of the tools listed in Activity Is This a Machine? Chart showing the types of levers with diagrams of each type Word tags: resistance, fulcrum, effort Here is a broom. Is a broom a machine? Is this shovel a machine? This crowbar and these tongs, are they machines? What about a fishing pole? How do we know when something is a machine? We said that a machine helps us in doing our work by helping us transfer or transform energy to do work. In this lesson, we are going to discover how each of these tools helps us in our work and why we say they are machines. At the Science Center, the students begin Part 1 of Activity Is This a Machine? At the Mathematics Center, the students complete Activity Seesaw Math. Students complete Part 2 of Activity Is This a Machine? At the Writing Center, students write the names of the tools in alphabetical order in their word bank. At the Library Center: 1. Students look for more examples of levers in magazines and books. They also include on their list tools found around the school or house. The students may refer to the chart showing the three types of levers with examples of each. The idea is that the students think through the examples in order to classify them, rather than memorize the specific definition of each type of lever. 2. Students read and discuss A Book About the Lever by H. Wade. 1. Name at least three jobs done around the house or school with levers. Describe the way the levers work. 2. Draw a seesaw; locate the fulcrum. Where are the resistance and the effort located? (The fulcrum is between the resistance and the effort; in this case either end of the seesaw is the effort or the resistance depending on the direction.)

23 Unit 3 Simple Machines 23 R R For example: One washer is at the end of a rod, but the fulcrum is placed so that the other end of the rod rests on the table. We can move the fulcrum so that the seesaw will balance (as best as possible since the wedge marks on the rod may not make for a perfect balance). Ask the students: Would this be a winning combination since there was one fewer washer used? The students discuss: What weight on the side opposite the washer made the seesaw balance? (The rod has weight that will balance against the washer.) 1. Draw a lever showing where you would place two objects in relation to the fulcrum to make them balance, one object of two pounds and one of four pounds. Label the type of balance your lever is and locate the fulcrum, the resistance and the effort. 2. The student selects an example of the lever she/he uses the most and writes about it, describing it, what type it is and how she/he uses it. 3. Look around the playground and at home and list and/or draw all the levers you can find. If you can, label their class. List of Activities for this Lesson Is This a Machine? Seesaw Math E E Closure and Assessment

24 24 Unit 3 Simple Machines ACTIVITY Is This a Machine? Objective The student identifies the force exerted to overcome the resistance in a given lever. Ball and bat; broom; shovel; crowbar; fishing pole; pliers; hedge clippers; tongs; paper cutter; tennis racket; garlic press; car jack; seesaw; hammer; wheelbarrow; hockey stick; tweezers; scissors; golf club; canoe and paddle; cart; nutcracker; bottle cap opener Procedures Part 1 Students examine each of the tools and then take turns demonstrating to the members of their groups how to use each tool. The students complete the parts of the chart labeled: Tool, Resistance, Force Used (Effort) and Work Done. 1. Determine the force overcome the resistance on each tool (for example, with the broom, the inertia of the dirt on the floor). 2. Determine the force used to overcome the resistance (the hand pushing on the broom handle). 3. Determine the work done (moving the dirt from one place to another). Tool Resistance Force Used (Effort) Work Done Fulcrum pliers nail hand squeezing on the handles pulled out the nail bolt on the pliers Part 2 Students complete the chart by locating the fulcrum for each lever. Tell students that a lever is one of the simplest machines man has invented. We have already examined some levers. The students name each of the tools examined in the activity. Ask students to see if the tools are alike and different in some ways. These are all levers, but they are somewhat different. After the students have had an opportunity to look for differences, help them organize the levers in some way. Suggest this: In a first-class lever, the fulcrum is between the load (resistance) and the effort (force). One example is the crowbar. The girl lifting the big rock exerts effort on one end of the bar, the rock is the resistance, and the small rock that provides a pivot is the fulcrum. In a second-class lever, the load or the resistance is between the fulcrum and the effort. One example is a nutcracker. The resistance is the nut, the effort is the hand pressing on the handles, but the fulcrum is the screw on the edge of the nutcracker.

25 Unit 3 Simple Machines 25 In a third-class lever, the effort is between the load and the fulcrum, as with a pair of tongs. First Class Second Class Third Class At the Art Center, the students make diagrams of tools showing where the resistance is located, and where the forced we use in work is located. Shovel Hammer

26 26 Unit 3 Simple Machines ACTIVITY Seesaw Math (The Game) Students construct the game and compete in groups of four. For each group: One yard-long dowel rod 1/2-inch diameter One empty 1/2-pint milk carton Several same-size and same-weight metal washers or counters with a hole that fits the dowel rod without slipping Preparation 1. Cut a wedge shape on a dowel rod (one yard in length) at its center. 2. Cut a wedge shape on the dowel every inch to the right and every inch to the left of the center wedge. Do not label the marks. After working with the seesaw, the students may want to label the marks. They may do so if that is one of their strategies to win the game. 3. Use the milk carton as the fulcrum by placing one of the wedges on the rod on top of the carton to form a seesaw. Before playing the game, the children: 1. explore and explain to each other what they did to make the seesaw balance 2. record their observations 3. discuss the rules with the other groups. The Game 1. The teacher demonstrates: Put the center cut on the fulcrum. Put washers on the seesaw on both sides to make it balance. Put three on one side and make the seesaw balance in different ways. 2. Place the washers at different distances from the fulcrum and again make the seesaw balance.

27 Unit 3 Simple Machines Tell the students that the rules of the game are these: each team has a complete set of washers, rod and carton the object of the game is for one team to place a set of three washers, say, on one side of the seesaw and another team (after team consultation) to place one more or one less washer on the opposite side to make the seesaw balance in only one attempt the first team to beat the challengers (the ones who place the washers) gets to set up the next set of washers and also to decide how many washers they will set up if the first team doesn t make the seesaw balance, the next team gets a turn, until a team wins. 4. Make some rules about how you can lift a heavy load. When you report to the entire class be sure you have reasons for your rules.

28 28 Unit 3 Simple Machines LESSON 4 A Bicycle BIG IDEAS A wheel and axle is a machine that rolls its load by decreasing friction. We can estimate a wheel s perimeter (circumference). Whole Group Work Encountering the Idea Exploring the Idea Books: Exploring Uses of Energy by E. Catherall, Let s Find Out About Wheels by M.C. Shapp, Wheels: A Tale of Trotter Street by S. Hughes and Unconventional Invention Book by B. Stanish Large, empty spool of thread; unsharpened pencil or a rod; scissors; lightweight cardboard box; balloon; box of drinking straws; 20 pencils; 20 marbles, same size Show students a wheel and axle consisting of the spool with the rod inserted in the center. Ask the students if they think it is a machine. Ask them if they think it is a lever. No, levers don t use a wheel. After a discussion, ask them to list the characteristics of a device that would help us decide if it is a machine. Although a machine requires that we exert effort, it is a device that still makes work easier. Can this wheel with the rod help us in our work? How? Is it easier to roll something than it is to pick it up and carry it? Before working at the learning centers, the students in a whole group activity make a Rolling Cart, as described below. Many of these materials can be brought from home. For each student: four empty spools of thread; two unsharpened pencils; an empty box (e.g. large matchbox); small objects to put in the box; masking tape or four to eight clamps; Super Glue Procedures 1. Put one pencil through the holes in two spools. 2. Put a clamp on the outside and inside of each spool to keep the pencil from moving from side to side. 3. Make a second axle with the other two spools and pencil. 4. Glue each end of the box to the length of one of the pencils.

29 Unit 3 Simple Machines 29 At the Mathematics Center: 1. Complete Activity Circumference of a Wheel. 2. Complete Activity Let s Get Even. Students need to be do this activity before the other activities in the Science Center to get the required background. 3. Complete Activity Average Speed. At the Science Center, the students have a choice to complete either or both racers. Complete Activity Tin Can Racers, and/or complete Activity Spool Racers. Read to the class Wheels: A Tale of Trotter Street. After reading and discussing the book, tell the students how a wheel and axle, another type of simple machine, has two parts, as the name says. One part of the machine is the wheel, and it has a shape like a circle. The other part is the axle, which has a shape like a cylinder. The wheels of a wheelbarrow are an example of a wheel and axle. Many times two wheels combine with one common axle to roll things from one place to another. An example is a donkey cart. Getting the Idea Axle Wheel Wheelbarrow Donkey Cart Show a picture of a bicycle. A bicycle is an example of a machine that has two wheels and two axles; it is not a simple machine, however. Ask the students to describe the bicycle. (Has two wheels; wheels turn on an axle; the chain looks like a belt on a pulley, etc.) What geometric shapes do you see in a bicycle? In a unicycle? At the Writing Center students make a list of the characteristics of a lever and of a wheel and axle. Add to this list as the students learn about other simple machines. They can choose a simple machine and write a poem or a riddle describing it. For added interest, the student can write the poem or riddle on the inside of a large outline of the selected machine. At the Library Center, students research the history of the wheel and report to their groups and to the class. The students also look for pictures of simple machines and name the various geometric shapes they see in the machines. Organizing the Idea

30 30 Unit 3 Simple Machines Applying the Idea At the end of the lesson, the students race the cars they construct by completing Activity Car Races. They have acquired all the understanding necessary to determine a racing winner. Closure and Assessment Problem Solving The student makes a list of things that roll or are circle-shaped. Then he/she selects one from the list and explores ways to use it as part of a wheel and axle. Student constructs a toy that uses a wheel and axle to move. List of Activities for this Lesson Tin Can Racers Spool Racers Circumference of a Wheel Let s Get Even Average Speed Car Races

31 Unit 3 Simple Machines 31 ACTIVITY Tin Can Racer Objective The student builds a racer from various objects found in the house and uses the racer to obtain data from which to make decisions. For each student or student group: Coffee can with the bottom intact and one or two plastic reclosing lids Large, strong rubber band or section cut from a bicycle inner tube Wooden dowel or sturdy chopstick; a smaller piece should be smaller than the diameter of the can bottom, and a larger piece should be approximately 10 cm long with one end rounded Metal washers Twine, wire or a twist tie Procedures To make the tin can racer: 1. Drill holes in the precise center of the coffee can bottom and plastic lids. The holes must be large enough so the rubber band will thread through them easily; the edge of the hole in the can bottom must be smooth so it won t cut the rubber band. 2. With the lids on the can, thread the rubber band through the holes so that its loops protrude from both ends of the can. 3. Push the shorter wooden dowel or stick through the loop of rubber band protruding from the can bottom. 4. Punch two small holes in the can bottom on either side of the stick and tie the stick securely to the can bottom with twine, wire or a twist tie. 5. Thread the other loop of the rubber band through the holes in several washers. There must be a sufficient number of washers to keep the longer stick, which is added in Step 6, from rubbing against the edge of the can. Later, you can increase or decrease the number of washers. 6. Place the longer wooden dowel or stick through the loop with the washers. To give the racer the needed energy to roll: Hold the can firmly in one hand and rotate the rod with the other hand. When the rubber band has wound tightly, the racer is ready to go. Students customize their racers with names, colors, slogans, etc.

32 32 Unit 3 Simple Machines ACTIVITY Spool Racers Objective The student builds a racer from various objects found in the house and alters the design of the racer to observe and discover the function of the different parts of the racer. For each student or student group: spool the size that holds 200 yards of sewing thread rubber band two wooden kitchen matches small chunk of soap with a hole cut through the middle and carved into a rough disk about four mm smaller than the flat end of the spool Procedures To make the spool racer: 1. Pass the rubber band through the center of the spool. 2. Through one end of the rubber band, firmly anchor a short piece of matchstick. Its length should be less than the diameter of the flat end of the spool. 3. Thread the other end of the rubber band through the hole in the disk-shaped piece of soap. 4. Place a longer piece of match stick (the stick minus the head) in the loop of the rubber band that you threaded through the disk of soap. To give the racer the needed energy to roll: Twist or wind up the rubber band by holding the spool firmly in one hand and rotating the stick with the other. Observations 1. Are the racers reliable? 2. What is the function of the soap? 3. Why is the longer match stick important? 4. What happens if we cut notches on the edges of the spools?